Spatial and Temporal Variations in Bacterial Macromolecule Labeling with [ methyl - ³ H]Thymidine in a Hypertrophic Lake

Abstract

The incorporation of [methyl-3H]thymidine into three macromolecular fractions, designated as DNA, RNA, and protein, by bacteria from Hartbeespoort Dam, South Africa, was measured over 1 year by acid-base hydrolysis procedures. Samples were collected at 10 m, which was at least 5 m beneath the euphotic zone. On four occasions, samples were concurrently collected at the surface. Approximately 80% of the label was incorporated into bacterial DNA in surface samples. At 10 m, total incorporation of label into bacterial macromolecules was correlated to bacterial utilization of glucose (r = 0.913, n = 13, P < 0.001). The labeling of DNA, which ranged between 0 and 78% of total macromolecule incorporation, was inversely related to glucose uptake (r =-0.823), total thymidine incorporation (r =-0.737), and euphotic zone algal production (r =-0.732, n = 13, P < 0.005). With decreased DNA labeling, increasing proportions of label were found in the RNA fraction and proteins. Enzymatic digestion followed by chromatographic separation of macromolecule fragments indicated that DNA and proteins were labeled while RNA was not. The RNA fraction may represent labeled lipids or other macromolecules or both. The data demonstrated a close coupling between phytoplankton production and heterotrophic bacterial activity in this hypertrophic lake but also confirmed the need for the routine extraction and purification of DNA during [methyl-3H]thymidine studies of aquatic bacterial production.

Bacterial production measured by leucine and thymidine incorporation rates in French lakes

“…All data were included except those obtained during the emptying period. and proteins (Robarts, Wicks & Sephton, 1986;Servais et al, 1987;Wicks & Robarts, 1987;Cho & Azam, 1988;Brittain & Karl, 1990;Jeffrey et al, 1990;Riemann & Bell, 1990;Torreton & Bouvy, 1991;Hollibaugh, 1993). Three extraction procedures are currently used to estimate the DNA contribution to total macromolecular labeling after thymidine incorporation: acidbase hydrolysis , phenolchloroform extraction (Wicks & Robarts, 1987) and enzymatic fractionation (Servais et al, 1987).…”

Biomass, production, and specific growth rate of bacterioplankton and coupling to phytoplankton in an oligotrophic lake

“…This extraction procedure measured [3H]TdR incorporated into RNA and DNA and avoided the major contaminant, protein (Herbert et al 197 1). Results are termed nucleic acid incorporation and should represent incorporation primarily into DNA, because 3H labeling of RNA is minimal during short incubations (Robarts et al 1986).…”

Visible light damage to Escherichia coli in seawater: oxidative stress hypothesis

“…The radioactivity of the samples was estimated with a Beckman L S 5000 E counter with, as reference, 20 nmol 1-' of the initial 3H methyl-thymidine solution directly set on a filter. The incubation times used in this method were too short to allow RNA labelling and therefore RNA synthesis was not evaluated (Robarts et a/. 1986;Moriarty 1986).…”